JP4417848B2 - Auxiliary light source and front light using the same - Google Patents

Abstract

To provide an assistant light source and a front-light emitting light to the light guide plate efficiently. A sectional shape of prism 14 a in the center of light stick is isosceles triangle having a tip angle (T°) of 100° and a tilt angle (a<SUB>1</SUB>) of 40°. The depth of the prism 14 a is D<SUB>1 </SUB>mum. A sectional shape of prism 14 b in a ¼ position from an end of light stick is triangle having a tip angle (T°) of 100° and a tilt angle (a<SUB>2</SUB>) of 34.8°. The depth of the prism 14 b is D<SUB>2 </SUB>mum. A sectional shape of prism 14 c in an end of light stick is triangle having a tip angle (T°) of 100° and a tilt angle (a<SUB>3</SUB>) of 24.05°. The depth of the prism 14 c is D<SUB>3 </SUB>mum.

Description

  The present invention relates to an auxiliary light source and a front light using the same, and more particularly to an auxiliary light source having a function of converting light from a point light source into a linear light source and a front light using the auxiliary light source.

  Reflective and transflective liquid crystal display devices have a liquid crystal cell composed of a pair of counter substrates and a liquid crystal layer sandwiched between the counter substrates, and display images using external light. It has a so-called reflection mode display function. This type of device includes a front light which is a surface illumination device that supplies light to the liquid crystal cell from the display side of the liquid crystal cell in order to perform a similar reflection mode display even when the outside light is weak.

  The front light is a light guide plate (light guide) arranged in parallel and facing the display side surface of the liquid crystal cell, and an edge light (side light) that is disposed on the end surface side and that makes light incident on the end surface. It is mainly composed of parts. The light from the edge light part propagates through the light guide plate, changes its propagation direction to the lower surface of the light guide plate facing the liquid crystal cell, that is, the display side surface of the liquid crystal cell, and enters the liquid crystal cell.

  The edge light is an auxiliary light source for the front light, and is an elongated cylindrical light stick for introducing light into the light guide plate, and a point light source that is disposed at both ends of the light stick and makes light incident on the light stick. And is composed mainly of. As this point light source, an LED is usually used. The edge light having such a configuration converts light from an LED, which is a point light source, into light of a line light source with a light stick, and guides the converted light to a light guide plate.

  The light stick in the edge light has a plurality of prisms formed on the surface opposite to the end surface of the light guide plate, and this prism allows the light of the edge light to enter the end surface of the light guide plate substantially perpendicularly ( JP 2001-345006 A (paragraph numbers [0004], [0005]).

  However, the present situation is that an edge light, which is a conventional auxiliary light source for a front light, cannot actually make light incident on the light guide plate substantially perpendicularly from the light emitting surface of the light stick. For this reason, in the conventional edge light, light cannot be efficiently incident on the light guide plate.

  The present invention has been made in view of such a point, and an object thereof is to provide an auxiliary light source capable of efficiently making light incident on a light guide plate and a front light using the auxiliary light source.

  The auxiliary light source of the present invention has a reflecting prism surface having a plurality of prisms and a light emitting surface facing the reflecting prism surface, and reflects the light by the reflecting prism surface while propagating the incident light therein. An elongated light stick that emits the light from an emission surface; and light generation means that is disposed at both ends of the light stick and generates light that is emitted to the light stick. The plurality of prisms include the light Each has a cross-sectional shape that takes into account the optical path of the direct light from the generating means and the reflected light reflected from the light generating means on the light exit surface.

  According to this configuration, the plurality of prisms formed on the reflecting prism surface of the light stick have cross-sectional shapes in consideration of the optical path of the direct light from the light generating unit and the reflected light reflected from the light generating unit on the light emitting surface, respectively. Therefore, not only the direct light from the light generating means but also the reflected light reflected by the light emitting surface from the light generating means can be emitted to the light guide plate substantially perpendicular to the light emitting surface, and as a result, the light stick Thus, light can be efficiently emitted to the light guide plate.

  In the auxiliary light source of the present invention, it is preferable that the cross-sectional shape is a substantially triangular shape having one tip angle and two tilt angles, and the angle of the tip angle is constant in each prism, and the tilt angles are different. .

  In the auxiliary light source of the present invention, it is preferable that the prism at the substantially central portion of the light stick has a substantially isosceles triangular cross-sectional shape.

In the auxiliary light source of the present invention, when the length of the light stick is L and the width of the light stick is W, the tip angle (T °) is preferably obtained by the following equation (1). .
T = 180-2 * (45-1 / 2 * tan < ^-1 > (3W / L)) ... Formula (1)

In the auxiliary light source according to the present invention, when the width of the light stick is W and the distance from the end of the light stick to the specific prism is X, a smaller inclination angle (a ( X) °) is preferably obtained by the following formula (2).
a (X) = 45−1 / 2 × tan ⁻¹ (W / 2X) (2)

In the auxiliary light source of the present invention, when the width of the light stick is W and the distance from the end of the light stick to the specific prism is X, the tilt angle closer to the end of the tilt angles. (A (X) °) is preferably obtained by the following equation (3).
a (X) = 45−1 / 2 × tan ⁻¹ (3W / 2X) (3)

  In the auxiliary light source of the present invention, the inclination angle (a (X) °) of the prism close to the end of the light stick is obtained by the equation (2), and the inclination angle of the prism close to the center of the light stick (a (X ) °) is preferably obtained by equation (3).

  In the auxiliary light source of the present invention, the inclination angle (a (X) °) of the prism, which is relatively greatly influenced by the direct light from the light generation means, is obtained by the equation (2), and the light emission surface from the light generation means It is preferable to obtain the inclination angle (a (X) °) of the prism, which has a relatively large influence of the reflected light reflected by the equation (3), using the equation (3).

  In the auxiliary light source of the present invention, it is preferable to make the inclination angle (a (X) °) of the prism in the region of X <2 mm constant.

In the auxiliary light source of the present invention, the depth (D μm) of the plurality of prisms is obtained by the following formulas (4) to (6), where N is the prism number from the end of the light stick. It is preferred that
(N = 1-17)
D (N) = 24.3 Formula (4)
(N = 18-28)
D (N) = 1.5 × N−1.2 Formula (5)
(N = 29-85) (Center of light stick)
D (N) = 0.6 × N + 24 (6)

  In the auxiliary light source of the present invention, it is preferable that a reflective metal film is formed on the reflective prism surface.

  In the auxiliary light source according to the present invention, the light stick is formed such that a prism using the inclination angle calculated by Equation (2) and a prism using the inclination angle calculated by Equation (3) are alternately formed. It is preferable to have the region Y.

  The front light of the present invention includes the auxiliary light source, and a light guide plate that emits light emitted from the auxiliary light source as light of a surface light source.

  According to this configuration, since the auxiliary light source can efficiently emit light to the light guide plate, it is possible to efficiently emit light to the liquid crystal cell.

  The liquid crystal display device of the present invention comprises a liquid crystal cell having a reflecting member and the front light for supplying light to the liquid crystal cell.

  According to this configuration, since the front light can efficiently emit light to the liquid crystal cell, the light use efficiency in the liquid crystal cell can be improved and the power consumption can be kept low.

  The present inventor uses light emitted to a light guide plate when the light is emitted to the light guide plate in an auxiliary light source composed of an elongated light stick having a reflecting prism surface and a light emission surface and light generation means arranged at both ends thereof. Of these, attention was paid to the fact that there is light that is emitted from the light generating means and directly reflected by the reflecting prism surface, and light that is emitted from the light generating means and reflected once by the light emitting surface and then reflected by the reflecting prism surface. . Then, the present inventor has found that two light beams can be efficiently emitted to the light guide plate by determining the cross-sectional shape of the prism in consideration of the tip angle and inclination angle of the prism and the depth of the prism. Invented.

  That is, the essence of the present invention comprises a light stick having a reflecting prism surface having a plurality of prisms and a light emitting surface opposite thereto, and a light generating means for generating light emitted to the light stick, and a plurality of light prisms. Auxiliary light source that allows light to be efficiently incident on the light guide plate by having a cross-sectional shape that takes into account the optical path of the direct light from the light generation means and the reflected light reflected from the light generation surface from the light generation surface, respectively. Is to realize.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a schematic configuration of a front light including an auxiliary light source according to an embodiment of the present invention.

  The front light shown in FIG. 1 includes an auxiliary light source including a light stick (light pipe) 11 having an elongated cylindrical shape, and LEDs 12 which are light generating means disposed at both ends of the light stick 11, and the auxiliary light source. The light guide plate 13 guides the light from the light to the liquid crystal cell.

  The light stick 11 has a reflecting prism surface 11a on the opposite side of the light guide plate 13, and further has a light emitting surface 11b on the opposite side of the reflecting prism surface 11a (side closer to the light guide plate 13). A plurality of prisms 14 (14a to 14c) are formed at a predetermined interval on the reflecting prism surface 11a. A reflective metal film for reflecting the light reflected from the LED 12 or the light emitting surface 11b is formed on the reflecting prism surface 11a. As the reflective metal film, a metal film such as an Al film can be used.

  When the line of the prism of the light stick 11 can be observed on the front light, the material of the light stick 11 may be mixed with diffusing particles such as metal particles having a high reflectance such as Al. Thereby, the light emitted from the light stick 11 can be broadened, and the lines of the prism can be made difficult to see. A diffusion sheet or the like may be disposed on the light exit surface 11b of the light stick 11 without mixing the diffusion particles into the material of the light stick 11.

  The cross-sectional shapes of the plurality of prisms 14 formed on the reflecting prism surface 11a are determined in consideration of the direct light from the LED and the optical path of the reflected light reflected from the LED on the light exit surface. That is, in FIG. 1, when the light from the LED 12 is emitted to the light guide plate 13, the light 15 directed directly from the LED 12 toward the reflecting prism surface 11a, and the reflecting prism surface 11a after being emitted from the LED 12 and once reflected by the light emitting surface 11b. There are two lights with the light 16 towards. In order to efficiently guide light to the light guide plate 13, it is necessary to determine the cross-sectional shape of the prism in consideration of these two optical paths.

  Thus, considering the optical path of the light 16 that is emitted from the LED 12 and once reflected by the light emitting surface 11b and then directed to the reflecting prism surface 11a, the length and width of the light stick 11 and the depth of the prism are the sectional shape of the prism 14. Will be affected. Therefore, in consideration of these factors, the sectional shape of the prism 14 formed on the reflecting prism surface 11a is individually determined.

For example, as shown in FIG. 1, the cross-sectional shape of the substantially central prism 14a is an isosceles triangle with a tip angle (T °) of 100 ° and an inclination angle (a ₁ ) of 40 °. The depth of the prism 14a is (D ₁ μm). Further, as shown in FIG. 1, the cross-sectional shape of the prism 14b at a position ¼ from the end of the light stick has a tip angle (T °) of 100 ° and an inclination angle (a ₂ ) of 34.8. ° is a triangle. The depth of the prism 14b is (D ₂ μm). As shown in FIG. 1, the cross-sectional shape of the prism 14c at the end of the light stick is a triangle having a tip angle (T °) of 100 ° and an inclination angle (a ₃ ) of 24.05 °. The depth of the prism 14c is (D ₃ μm). That is, the front end angle of the prism 14 is constant for all the prisms, and the inclination angle of the prism 14 is set to increase from the side closer to the LED 12 toward the center. Further, the depth of the prism is set so as to increase from the side closer to the LED 12 toward the center.

  The tip angle, tilt angle, and depth of the prism 14 can be obtained based on the following equations. These equations are obtained in consideration of the optical path of the light 16 that is emitted from the LED 12 and once reflected by the light emitting surface 11b and then toward the reflecting prism surface 11a. Thereby, the cross-sectional shape of each prism 14 is calculated | required separately.

The tip angle (T °) is obtained by the following equation (1). Here, the length of the light stick is L, and the width of the light stick is W.
T = 180-2 * (45-1 / 2 * tan < ^-1 > (3W / L)) ... Formula (1)

The smaller inclination angle (a (X) °) of the inclination angles is obtained by the following equation (2). Here, the width of the light stick is W, and the distance from the end of the light stick to the specific prism is X.
a (X) = 45−1 / 2 × tan ⁻¹ (W / 2X) (2)

Further, the smaller inclination angle (a (X) °) of the inclination angles is obtained by the following equation (3). Here, the width of the light stick is W, and the distance from the end of the light stick to the specific prism is X.
a (X) = 45−1 / 2 × tan ⁻¹ (3W / 2X) (3)

  The above formulas (2) and (3) are both the tilt angle (a (X) °) of the prism, and the formula (2) is the tilt angle of the prism (a ( X) °), and Equation (3) is a formula for calculating the inclination angle (a (X) °) of the prism when the reflected light reflected from the light exit surface from the LED is taken into account.

  In the light stick, the effect of direct light is relatively large near the end of the light stick, and the effect of reflected light is relatively large in the center of the light stick. Therefore, the inclination angle (a (X) °) of the prism is calculated using the formula (2) or the formula (3) as appropriate depending on the magnitude of the influence of the direct light or the reflected light. That is, the inclination angle (a (X) °) of the prism near the end of the light stick is obtained by the equation (2), and the inclination angle (a (X) °) of the prism near the center of the light stick is obtained by the equation (3). Ask for.

  In the region closer to the end of the light stick with X <2 mm, the inclination angle (a (X) °) of the prism may be constant. If the tilt angle of the prism (a (X) °) is too small, it becomes difficult to process the light stick, so the prism tilt angle (a (X) °) in the region closer to the end of the light stick is kept constant. By doing so, the processing of the prism into the light stick can be facilitated.

The depths (D μm) of the plurality of prisms are obtained by the following formulas (4) to (6). Here, the number of the prism from the end of the light stick is N.
(N = 1-17)
D (N) = 24.3 Formula (4)
(N = 18-28)
D (N) = 1.5 × N−1.2 Formula (5)
(N = 29-85) (Center of light stick)
D (N) = 0.5 × N + 24 Formula (6)

  In the auxiliary light source having the above-described configuration, the light from the LED 12 is reflected by the reflecting prism surface 11 a while propagating in the light stick 11 and is emitted from the light emitting surface 11 b to the light guide plate 13. In this case, the reflecting prism surface 11a is formed with prisms each having a cross-sectional shape that takes into account the optical path of the direct light from the LED and the reflected light reflected from the light exit surface of the LED, so only the direct light from the LED is formed. In addition, the reflected light reflected by the light exit surface from the LED can be emitted to the light guide plate almost perpendicularly to the light exit surface, and as a result, light can be efficiently emitted from the light stick to the light guide plate. It becomes. Further, since the auxiliary light source can efficiently emit light to the light guide plate, it is possible to efficiently emit light to the liquid crystal cell.

  Next, examples performed for clarifying the effects of the present invention will be described.

  2 is a diagram for explaining the position of the prism of the auxiliary light source according to the embodiment of the present invention, FIG. 3 is an enlarged view of a portion A in FIG. 2, and FIG. 4 is a diagram B in FIG. It is an enlarged view of a part.

  The light stick 11 shown in FIG. 2 has 169 prisms 14 on the reflecting prism surface. Numbers of the prisms 14 are given as N = 1, 2,..., 84, 85 from the end of the light stick 11 toward the center. The length of the light stick 11 is 59.2 mm, and the width of the light stick 11 is 3.5 mm. The pitch between the prisms is constant at 0.35 mm.

  In such a light stick 11, the cross-sectional shape of the prism 14 is determined by obtaining the tip angle, the inclination angle, and the depth from the above formulas (1) to (6). For example, the tip angle is constant at 100 °, and the inclination angle is prism No. 1 at 24.05 °, prism no. It is 40 degrees at 85. The depth is prism No. 1 and 24.3 μm. 85 is 75 μm.

  The auxiliary light source having the light stick 11 shown in FIG. 2 was analyzed by simulation to determine whether light was emitted perpendicular to the light guide plate. Specifically, the light emitted in the vertical direction was evaluated by obtaining the intensity (cd) as a parameter. In this case, as shown in FIG. 5, when tilted to the right from the vertical direction (0 °), it was defined as (+), and when tilted to the left from the vertical direction (0 °), it was defined as (−).

Further, as a comparative example, as shown in FIG. 7, a plurality of prisms having different depths (h ₁ to h ₃ ) but similar cross-sectional shapes (tip angle 120 °, tilt angle 30 °). A simulation was performed in the same manner as described above for the auxiliary light source including the light stick 21 having the light source and the LED 22 disposed at the end thereof.

  As a result of the simulation, as is clear from FIG. 6, the auxiliary light source of the present invention can emit light from the LED 12 substantially vertically. Moreover, it turns out that the intensity | strength is also high as a whole. Therefore, the auxiliary light source of the present invention has a large amount of light and can efficiently emit light to the light guide plate. On the other hand, as is apparent from FIG. 8, the auxiliary light source of the comparative example has light shifted to the right by about 10 ° and has a relatively low intensity. For this reason, light cannot be efficiently emitted to the light guide plate as an auxiliary light source.

  Next, a case where a front light having such an auxiliary light source is applied to a liquid crystal display device will be described. FIG. 9 is a cross-sectional view illustrating a schematic configuration of a liquid crystal display device including a front light having an auxiliary light source according to the present invention.

  Here, a case where the liquid crystal display device is a reflective liquid crystal display device will be described. In FIG. 9, there are actually electronic elements and optical elements such as electrodes and color filters, but these are omitted for the sake of simplicity.

  The liquid crystal display device shown in FIG. 9 mainly includes a liquid crystal cell 33 and a front light 30 that is a surface illumination device that supplies light to the liquid crystal cell 33. The front light 30 mainly includes an auxiliary light source 31 according to the present invention and a light guide plate 32 that guides light from the auxiliary light source 31 to the liquid crystal cell 33.

  The light guide plate 32 has a shape in which mountain-shaped portions and valley-shaped portions are alternately repeated. In this example, this shape has a relatively large area and a relatively gentle inclined surface relatively with respect to the extending direction of the light guide plate and a relatively steep and relatively steep surface with respect to the extending direction. It is formed by an alternate combination with an inclined surface. The longitudinal direction (groove direction) of the grooves formed between adjacent mountain-shaped portions is substantially orthogonal to the extending direction of the light guide plate 32.

  The liquid crystal cell 33 is mainly composed of a pair of glass substrates 33a and 33c disposed to face each other and a liquid crystal layer 33d sandwiched therebetween. A reflector 33b, which is a light reflecting member, is provided in a region on one glass substrate 33a and in contact with the liquid crystal layer 33d. A metal thin film or the like can be used as the reflector 33b, and these metal thin films can be formed on the glass substrate 33b by a physical method such as sputtering.

  A polarizing plate 33e is disposed on the surface of the other glass substrate 33c that is not in contact with the liquid crystal layer 33d. This polarizing plate 33e can be arrange | positioned by sticking on the surface of the glass substrate 33c. In addition, about the liquid crystal cell 33, the thing similar to what is used in a reflection type liquid crystal display device can be used.

  The liquid crystal cell 33 configured as described above is arranged at a predetermined interval from the front light 30. That is, the liquid crystal cell 33 and the front light 30 are disposed so that the surface of the polarizing plate 33 e of the liquid crystal cell 33 faces the light emitting surface of the front light 30.

  In the liquid crystal display device having the above configuration, light emitted from the LED of the auxiliary light source 31 is reflected inside the light stick by the light stick reflection film and emitted to the light guide plate 32.

  Light from the front light 30 enters the end face of the light guide plate 32. The light guide plate 32 propagates the incident light inside. In this propagation process, light is reflected on the steep slope of the light guide plate 32 to change the propagation direction greatly, and is emitted from the bottom surface (light emitting surface) of the light guide plate 32 toward the liquid crystal cell 33.

  The light emitted from the front light 30 passes through the polarizing plate 33e, the glass substrate 33c, and the liquid crystal layer 33d, is reflected by the reflector 33b, passes through the liquid crystal layer 33d, the glass substrate 33c, and the polarizing plate 33e, and further passes through the front light. The light is emitted to the outside through 30 light guide plates 32. As a result, display in the reflection mode is performed.

  As described above, in the liquid crystal display device including the front light having the auxiliary light source according to the present invention, the auxiliary light source can efficiently emit light to the light guide plate, so that the light is efficiently emitted to the liquid crystal cell. Thereby, the light utilization efficiency in the liquid crystal cell is improved, and the power consumption can be kept low.

  As described above, the present invention obtains a tilt angle that depends on the distance from the end of the light stick to the particular prism according to Equation (2) or Equation (3). In this case, as shown in FIG. 10, there is a prism position (X in FIG. 10) where the inclination angle changes drastically. At this time, as shown in FIG. 11, the adjustment region Y in which the prism using the inclination angle calculated by the equation (2) and the prism using the inclination angle calculated by the equation (3) are alternately formed. It is preferable to have it. With such an adjustment area Y, the uniformity of light can be improved for the entire light stick.

  This adjustment area Y preferably has a distance X between 5 mm and 15 mm from the end of the light stick to the specific prism. For example, as shown in FIG. 2, when the prism number at the center is 85, the adjustment region Y preferably has from about 15 prism numbers to about 40 prism numbers.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, the numerical values used for the tip angle and inclination angle of the prism, the numerical value of the prism pitch, the numerical value of the prism depth, and the number of prisms in the above embodiment are not particularly limited, and may be changed as appropriate. Is possible. As for the angle, the allowable range can be about ± several degrees with respect to the set value.

  Further, the formula in the above embodiment is a light stick having a length of about 60 mm (for PDA). For other uses, it is necessary to obtain a separate formula in consideration of two optical paths. However, the present invention can be applied even if the light stick length is other than 60 mm.

  Although the case where the present invention is applied to a front light is described in the above embodiment, the present invention can also be applied to a backlight.

  As described above, according to the present invention, the plurality of prisms formed on the reflecting prism surface of the light stick consider the optical path of the direct light from the light generating unit and the reflected light reflected from the light generating unit on the light emitting surface. Each has a cross-sectional shape. For this reason, not only the direct light from the light generation means but also the reflected light reflected from the light emission surface from the light generation means can be emitted to the light guide plate substantially perpendicular to the light emission surface, and as a result, the light stick Thus, light can be efficiently emitted to the light guide plate.

It is a figure which shows schematic structure of the frontlight provided with the auxiliary light source which concerns on embodiment of this invention. It is a figure for demonstrating the position of the prism of the auxiliary light source which concerns on embodiment of this invention. It is an enlarged view of the A section in FIG. It is an enlarged view of the B section in FIG. It is a figure for demonstrating the left-right angle at the time of investigating the effect of the auxiliary light source which concerns on embodiment of this invention. It is a figure which shows the result of the left-right angle of the auxiliary light source which concerns on embodiment of this invention. It is a figure for demonstrating the prism of the auxiliary light source of a comparative example. It is a figure which shows the result of the left-right angle of the auxiliary light source of a comparative example. It is sectional drawing which shows schematic structure of the liquid crystal display device provided with the front light which has the auxiliary light source of this invention. Fig. 5 shows a change in tilt angle in an auxiliary light source according to the present invention. 3 shows an adjustment area in an auxiliary light source according to the present invention.

Claims (11)

It has a reflecting prism surface having a plurality of prisms and a light emitting surface opposite to the reflecting prism surface, and reflects the light by the reflecting prism surface while propagating the incident light therein, and emits the light from the light emitting surface. An elongated light stick, and light generating means disposed at both ends of the light stick for generating light emitted to the light stick, wherein the plurality of prisms include direct light from the light generating means and the cross-sectional shape in consideration of the optical path of light reflected by the light exit surface from the light generating means possess respectively,
The cross-sectional shape is a substantially triangular shape having one tip angle and two tilt angles, the tip angle is constant in each prism, the tilt angles are different, and
When the width of the light stick is W and the distance from the end of the light stick to a specific prism is X,
The smaller inclination angle (a (X) °) of the inclination angles is obtained by the following equation (2), or the inclination angle closer to the end (a (X) °) of the inclination angles (a (X) °) Is obtained by the following formula (3).
a (X) = 45−1 / 2 × tan ⁻¹ (W / 2X) (2)
a (X) = 45−1 / 2 × tan ⁻¹ (3W / 2X) (3) The auxiliary light source according to claim 1, wherein the prism at the substantially central portion of the light stick has a cross-sectional shape of a substantially isosceles triangle. The length of the light stick is L, the width of the light stick is W, claim 1 or claim, characterized in that the tip angle (T °) is obtained by the following equation (1) 2. The auxiliary light source according to 2 .
T = 180-2 * (45-1 / 2 * tan < ^-1 > (3W / L)) ... Formula (1) The inclination angle (a (X) °) of the prism near the end of the light stick is obtained by the equation (2), and the inclination angle (a (X) °) of the prism near the center of the light stick is obtained by the equation (3). The auxiliary light source according to claim 1 , wherein the auxiliary light source is obtained by: The inclination angle (a (X) °) of the prism that has a relatively large influence of the direct light from the light generating means is obtained by the equation (2), and the influence of the reflected light reflected from the light emitting surface from the light generating means is The auxiliary light source according to any one of claims 1 to 3, wherein an inclination angle (a (X) °) of a relatively large prism is obtained by an expression (3). The auxiliary light source according to any one of claims 1 to 5, wherein an inclination angle (a (X) °) of a prism in a region where X <2 mm is constant. The depth of the plurality of prisms (Dimyuemu) are claims, characterized in that the number of prisms from an end of the light stick when the N, is determined by the following equation (4) to (6) The auxiliary light source according to any one of claims 1 to 6 .
(N = 1-17)
D (N) = 24.3 Formula (4)
(N = 18-28)
D (N) = 1.5 × N−1.2 Formula (5)
(N = 29-85) (Center of light stick)
D (N) = 0.6 × N + 24 (6) The auxiliary light source according to claim 1, wherein a reflective metal film is formed on the reflecting prism surface. The light stick has an adjustment region Y in which a prism using the inclination angle calculated by Equation (2) and a prism using the inclination angle calculated by Equation (3) are alternately formed. The auxiliary light source according to any one of claims 1 to 8 . A front light comprising: the auxiliary light source according to any one of claims 1 to 9; and a light guide plate that emits light emitted from the auxiliary light source as light of a surface light source. A liquid crystal display device comprising: a liquid crystal cell having a reflective member; and the front light according to claim 10 for supplying light to the liquid crystal cell.

Images